who studied in Alexandria
and later founded a somewhat successful community
based on the principles of Plato
Plotinus is most widely known for founding the Neoplatonic School and for his theory of emanation: the idea that all reality and all existence proceeds from a central point which is and must be an eternally present and eternally perfect being ("the one" - hen). By Plotinus' construction, the further a given thing is from "the one" the less unification and perfection that thing possesses. Matter and the physical state are the furthest from "the one", while intellect is closest to "the one".
The Enneads of Plotinus were compiled posthumously by his students, most notably Porphyry who contributed a biography of Plotinus to the treatises.